Variable resistors



1964 R. H. DUTTON ETAL 3,122,573

VARIABLE RESISTORS Filed June 24, 1960 2 Sheets-Sheet 1 INVENTORS' RICHARD H. DUTTON NEIL MAG GREGOR ATTORNEY Feb. 25, 1964 R. H. DUTTON ETAL 3,122,673

VARIABLE RESISTORS Filed June 24, 1960 2 Sheets-Sheet 2 53 362%? QAWTOOTH 52 GENERATOR 55 (6/ 2 PHASE I NEW 1 l 59 AZIMUTH -"*-T MOTOR 58 MULT'AR 5 l 63 AMPLIFIER 48 1 POT L a 5/ RANGE 4 57 l MULTIAR R I 63b FLIP FLoP-- PULSE GOINCIDENCE GATE STRETCHER x a 3 65/ VERTICAL SWEEP GENERATOR 86 l r I Q SINE E PULSE MULTIAR +STRETGHER 60 I 86 cos. S- COINGIDENCE GATE as A f 52 "\r 5 ll F/G. 5 HORIZONTAL SWEEP 8/ GENERATOR //vv/vr0/?s RICHARD H. DU TTON NEIL MAG 6/7560 P m A 7' TOR/V5) United States Patent 3,122,673 VARIABLE RESISTORS Richard H. Dutton, Hoiliston, and Neil MacGregor, Newton Center, Mass, assignors to Raytheon Company, Lexington, Mass., a corporation of Delaware Filed time 24, 196%), Ser. No. 38,515 6 (ilaims. (Cl. 315-22) This invention relates to variable resistors adapted to be varied together both by radial and angular displacement.

In certain operations such as the manual selection and marking of one or more of several targets on a radar display it is desirable to have means for simultaneously varying the radial and angular displacement of the target marker on the display. This can be done conveniently by varying two resistors, one by radial movement and the other by angular movement. In the past, the resistors have been varied by means of the so-called joystick control which consists of a handle engaging movable registor arms and pivoted for rotation in two degrees of freedom about a spherical surface by means of a gimbal system. The gimbal system requires high precision machining in its construction and, therefore, is costly. Furthermore, the joystick protruding from a control panel may be unintentionally moved from its set position.

These difficulties are avoided by the construction of the present invention which employs at least one resistance variable by the angular displacement of electrical contacts engaging resistors. The contacts are carried by a rotatable knob which also carries at least two other contacts. These other contacts engage, for example, a circular resistance card so that the resistance between the contact and one end of the card is dependent upon the radial position of the contact. One contact engaging the resistance card is radially fixed while the other may be moved radially by a knurled wheel which is preferably mounted on the knob. As a result, the resistance between the fixed and radially movable contacts engaging the card is representative of the radial position of the radially movable contact as established by the position of the knurled wheel.

An operator may rotate the knurled wheel with a finger, to represent a selected radial position, while at the same time rotating the knob with the rest of the hand to represent a selected angular position or azimuth. The variable resistors controlled by knob rotation and the resistance between the contacts engaging the card may be used, for example, to control the position at which the beam of a plan position indicating (P.P.I.) cathode ray tube display brightens to provide an identifying mark for a target on the display. Thus, the device can be used for the same purpose as the so-called joystick but requires no precise machining to manufacture. Simple relatively inexpensive techniques may be employed to manufacture the device. For example, the movable contacts may be made to stay in position once adjusted by employing simple locking or friction devices. But most important, simple scale markings can be used to directly indicate displacements instead of the expensive, bulky external counter often required for this purpose by the conventional joystick controls.

The invention will be better understood from the following specific descriptions taken with reference to the drawings in which:

FIG. 1 is a plan view of an embodiment of the invention;

FIG. 2 is a sectional view taken at section 22 shown in FIG. 1;

FIG. 3 is a schematic diagram of a display system in 3,122,673 Patented Feb. 25, 1964 which one embodiment of the present invention could be used;

FIG. 4 is a diagrammatic view of the face of the cathode ray tube of the display system of FIG. 3;

FIG. 5 is a schematic diagram of another display system in which another embodiment of the present invention could be used; and

FIG. 6 is a diagrammatic view of the face of the cathode ray tube of the display system of FIG. 5.

In FIGS. 1 and 2, reference numeral 10 designates a potentiometer which is rotatably supported in a bracket 12 and driven by a knob 13, adapted to be turned by the operators hand. The knob 13 fits within an opening 14 in a panel 15. The opening 14 is surrounded by a compass rose 16 or other indication of direction such as a 360 scale of angles. A slot 17 is formed in the knob 13 arranged along a radius of the knob. A second scale 18 is inscribed along one side of this slot indicating the intervals of range to be represented by the displacement of range potentiometer 20 which is supported on the knob 13 directly below the slot 17.

This range potentiometer 20 is shown with a circular resistance card 21 having an opening 22 at the center to accommodate the shaft 11. The knob 13 carries a fixed contact 23 and a movable contact 24. The movable contact 24 is preferably supported from a shaft 25 carrying a pinion gear 26 engaging and supported on a rack 27 mounted on the knob 13, so as to be aligned with the slot 17. A knurled wheel 28 is mounted on the shaft 25 and fixed thereto. Wheel 28 is made large enough in diameter to protrude somewhat through the slot and beyond the outer surface of the knob so it may be rolled back and forth along the slot by one finger of the operators hand as he turns the knob. An arrow 30 is inscribed on the knob at the outer end of the slot 17.

In operation where the device is used to mark a particular one of several targets represented on a P.P.I. display, the operator turns the knob with his hand until the arrow 3i) points to the marking on the scale 16 corre sponding to the azimuth of the desired target and the knurled wheel 28 is turned until the center of the wheel is below the inscribed range marking on the scale 18 corresponding to the range of the desired target. As the azimuth and range of the desired target, as indicated on the P.P.I. display, varies, the knob 13 and wheel 28 may be turned to keep the arrow 30 and the center of the wheel 28 at the positions corresponding to these varying azimuths and ranges. Thus, the marker signal may be made to accurately follow the shifting positions of the desired target on a P.P.I. display by means of appropriate circuitry coupling the device to the display.

The resistance card of the range potentiometer has been shown and described as circular with a central opening fixed to the panel. It could be a strip of material carried by the knob. In this case provision would have to be made to carry current to the fixed contact of the potentiometer during its rotation as well as to the movable contact. A slip ring could serve this purpose.

While the circuitry for a display includes potentiometer controls which form a part of this invention, the parts directly involving the potentiometer controls will be briefly described to show how the device of the invention can be applied in such apparatus.

A P.P.I. display system utilizing the device of the invention in which the rotary potentiometer is of the standard 360 type is shown in FIGS. 3 and 4. The reference numeral 40 in FIG. 3 designates such a standard 360 potentiometer hereinafter referred to as the azimuth potentiometer with one terminal 41 connected through a resistor 42 to a source of positive potential 43 and the other terminal 44 connected through a resistor 45 to a source of negative potential 46. The rotating contact 47 3 is connected to an input of azimuth multiar circuit 48. The range potentiometer 49 is connected between the terminals 41 and 44 and the moving contact 54) of this range potentiometer is connected to range multiar cir cuit 51.

Multiar circuits are widely used for amplitude comparison producing a pulse or step output when the amplitude of input waveforms are equal or at a predetermined ratio to each other. A suitable multiar circuit employing a diode selector and regenerative amplifier is described on page 343, volume 19 of Radiation Laboratory Series published by McGrawJ Iill Book Company.

Other inputs to multiar circuits 48 and 51 are derived from P.P.I. system 52 which may be a typical resolversweep P.P.I. system such as described on page 535, volume l of the Radiation Laboratory Series. System 52 might, for example, consist of a radar pulse generator 53, energizing radial sweep sawtooth generator 54 which energizes the rotor coil of two phase resolver 55. The rotor coil is mechanically rotated by coupling to the radar antenna drive motor 56 which directs the radar antenna in azimuth. As a result, each of the field coils of resolver 55 produce sine and cosine modulated signals, modulated at the rate of antenna rotation and suitable for driving orthogonal deflection coils 57 and 58 of cathode ray tube P.P.I. display 59. Amplifiers 6i and 61 serve to control the size of the display.

The input from system 52 to azimuth multiar 48 is representative of P.P.I. azimuth and is obtained from potentiometer 62 driven by antenna drive motor 56. Potentiometer 62 is preferably identical to potentiometer 40 and energized by the same potentials. Consequently, the output from azimuth multiar 48 is a pulse occurring when the output amplitudes from potentiometers 40 and 62 are equal. The pulse from azimuth multiar 48 indicates that the azimuth setting of rotary contact 47 of potentiometer 49 is the same as the P.P.I. system antenna azimuth.

The input to range multiar circuit 51, derived from system 52, preferably comes from the output of sawtooth wave generator 54 which is triggered by radar pulse generator 53. The amplitude of the sawtoothwave represents range P.P.I. sweep and is compared with the output of range potentiometer 49. When these'outputs are equal, range multiar circuit 51 produces a pulse. The interval between a pulse from radar pulse generator 53 and the subsequent pulse from multiar circuit 51 represents 'a portion of P.P.I. range sweep indicative of the position and output of range potentiometer 49. The'out'put from pulse generator 53 and the output from range multiar circuit 51 are applied to stages 63a and 63b, respectively, of double input bistable flip-flop circuit 63. Consequently, the output from stage 63a is a pulse coincident withan equal to the interval and may serve to control intensity of a P.P.I. display 59. It is only necessary that the pulse output from stage 63a be gated to be substantially coincident with the output of azimuth multiar circuit 48 before ap plication to the intensity control of P.P.I. display 59. Pulse stretcher circuit 64 and coincidence gate 65 are provided for this purpose.

Pulse stretcher circuit 64 might, for example, be a one shot multivibrator producing a gating pulse of given predetermined interval when triggered by the output of azimuth multiar 48. This interval preferably exceedsthe interval between two or more successive sawtooth pulses from generator 54. The output of pulse stretcher 64 and the output of stage 63a are applied to coincidence gate 65 which energizes intensity control grid 66 of display 59. The intensity control grid 66 is, therefore, energized while the electron beam of display tube 59 sweeps radially at least once at the azimuth selected by rotary contact 47 of rotary potentiometer 40. The interval the beam is energized during such radial sweep or sweeps is representative of the range selected by moving contact 50 of range potentiometer 49. The radial line thus formed on the face of P.P.I. display tube 59 is sometimes called a cursor line and serves to precisely identify a given azimuth and range on the display, for example, the azimuth and range of a target appearing thereon.

FIG. 4 shows the cursor line 67 which appears on the face of tube 59 and is controlled by potentiometers 4t) and 49 for establishing azimuth and range to a target 68 appearing thereon.

Another display system utilizing the device of the invention in which the potentiometer is of the sine-cosine type is shown in FIGS. 5 and 6. The reference 70 in FIG. 5 designates a symbolic representation of a sine-cosine potentio meter used with the device of the invention. The reference symbol 4 9 desi nates the range potentiometer which preferably operates as already described with reference to FIGS. 1 and 2. Reference 56 designates the moving contact preferably controlled as already described with reference to movable contact 24 shown in FIG. 2.

One terminal 71 of sine-cosine potentiometer 7% is connected through a resistor '72 to a source of positive potential 73. The other terminal 74 is connected through a resistor 75 to a source 76 of negative potential. One movable contact 77 producing a voltage representing the sine function is applied to the input of sine multiar circuit 78. The other input to sine multiar circuit 78 is a sawtooth wave obtained from the vertical sweep generator 80 providing the vertical sweep to cathode ray tube display 81. Vertical sweep generator 3% together with horizontal sweep generator 82 energize, for example, pairs of deflection plates 83 and 84 in display tube 81 to provide a television type raster on the face thereof.

The voltage 'at the second contact 84 representing the cosine function acts as the reference voltage for cosine multiar circuit 85.

If the raster of tube 81 is formed by interlaced odd and even numbered horizontal lines, as is often the case, the pulse output of sine multiar 78 must be frequently divided by two for reasons which will be apparent. Consequently, the pulse output of sine multiar circuit 78 is applied to frequency divider 86 which selects alternate pulses. v

The pulse output from divider 86 is applied to pulse stretcher 87 producing a pulse width substantially equal to the interval of a horizontal line of the raster. The output of cosine multiar and pulse stretcher 87 are applied to coincidence gate 88 which is coupled to grid 89 controlling the beam intensity of display tube 81. Such control obviously produces a bright spot on the face of display 81when'the beam reaches a point in its raster representing the position of the desired target selected by mechanical manipulation of range and azimuth potentiometers 49 and 70.

If the interlaced type scan is employed and the output of multiar 78 is not frequency divided, then the bright spot produced on the face of tube 81 appears on both odd and even numbered lines which of course are scanned alternately and are positioned one line apart. As a result definition suffers and annoying flicker is introduced.

FIG. 6 shows the face of tube 81, the bright spot 90 being positioned depending on the range and azimuth selected by potentiometers 49 and 70 respectively. Thus by the use of the potentiometer of the present invention shown in FIGS. 1 and 2, a target marker for a television type display of, for example, a radar picture, can be produced in a convenient, inexpensive and reliable manner.

While there is described herein preferred embodiments of the present invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without deviating from the spirit or scope of the invention as set forth in the appended claims.

What is claimed is:

l. A system for producing marks at selected locations on a cathode ray tube display comprising a cathode ray tube having beam forming, beam deflecting and beam modulating means, a plurality of variable resistors, shaft means to vary at least one of said resistors by rotary motion, a knob mounted on said shflt, means mounted on said knob to vary at least one of the remaining resistors by the radial displacement of an electrical contact, and means coupled to said resistors and said deflecting means to produce a voltage pulse at the modulating means of said cathode ray tube at a time said beam sweeps through said selected location.

2. A system for producing marks at selected locations on a cathode ray tube display comprising a cathode ray tube having beam forming, beam deflecting and beam modulating means, a plurality of variable resistors, shaft means to vary at least one of said resistors by rotary motion, a knob mounted on said shaft coaxially therewith, said one resistor being arranged as a sine and cosine potentiometer, means to vary at least one of the remaining resistors by the radial displacement of an electrical contact, means to mount said contact on said knob whereby said contact is movable radially therefrom and means coupled to said resistors and said doflecting means to produce a voltage pulse at the modulating means of said cathode ray tube at a time corresponding to said selected locations.

3. A system for producing marks on a cathode ray tube display designating a particular target comprising a cathode ray tube, having beam forming, beam deflecting and beam modulating means, a plurality of variable resistors, shaft means to vary at least one of the said resistors by rotary motion, a knob mounted on said shaft means, means supponted on said knob to vary at least one of the remaining resistors by the radial displacement 01f an electrical contact, deflecting means to produce a voltage pulse at the modulating means of said cathode ray tube at a time corresponding to the desired location of the marks.

4. A system for producing marks on a cathode ray tube display designating a particular target comprising a cathode ray tube, having beam (forming, beam deflecting and beam modulating means, a plurality of variable resistors, shaft means to vary at least one of the said resistors by rotary motion through a complete revolution, a knob mounted on said shaft means, means supported on said knob tovary at least one of the remaining resistors by the radial displacement of an electrical contact and means coupling said resistors to said deflecting means and said modulating means whereby said marks are produced on said cathode ray tube display.

5. A system for producing marks on a cathode ray tube display designating a particular target comprising a cathode ray tube, having beam forming, beam deflecting and beam modulating means, a plurality of variable resistors, shaft means to vary at least one of said resistors by rotary motion, said resistor being arranged as a sine and cosine potentiometer, a knob mounted on said shaft means, means supported on said knob means to vary at least one of the remaining resistors by the radial dis placement of an electrical contact and means coupling said resistors to said deflecting means and said modulating means whereby said marks are produced on said cathode ray tube display.

6. A combination of variable resistors comprising at least one resistor "formed in an arc, a shaft concentric with said are for varying said one resistor by rotary motion, a knob mounted on said shaft concentric therewith for imparting said rotary motion thereto, and at least one remaining variable resistor including a fiXed member and a movable member, said movable member being mounted on said knob and movable radially with respect to said knob.

References Cited in the file of this patent UNITED STATES PATENTS 1,660,161 Hansen Feb. 21, 1928 2,422,697 Meaoham June 24, 1947 2,603,775 Chipp July 15, 1952 2,797,411 Watson June 25, 1957 2,986,361 Codding May 30, 19611 

1. A SYSTEM FOR PRODUCING MARKS AT SELECTED LOCATIONS ON A CATHODE RAY TUBE DISPLAY COMPRISING A CATHODE RAY TUBE HAVING BEAM FORMING, BEAM DEFLECTING AND BEAM MODULATING MEANS, A PLURALITY OF VARIABLE RESISTORS, SHAFT MEANS TO VARY AT LEAST ONE OF SAID RESISTORS BY ROTARY MOTION, A KNOB MOUNTED ON SAID SHAFT, MEANS MOUNTED ON SAID KNOB TO VARY AT LEAST ONE OF THE REMAINING RESISTORS BY THE RADIAL DISPLACEMENT OF AN ELECTRICAL CONTACT, AND MEANS COUPLED TO SAID RESISTORS AND SAID DEFLECTING MEANS TO PRODUCE A VOLTAGE PULSE AT THE MODULATING MEANS OF SAID CATHODE RAY TUBE AT A TIME SAID BEAM SWEEPS THROUGH SAID SELECTED LOCATION. 